Recently, a receiving device capable of receiving a wireless signal transmitted from a satellite is mounted on a mobile body such as a car or a mobile telephone. According to a Global Positioning System (GPS) measurement, it is possible to estimate the location of a mobile body on which such a receiving device is mounted. A location estimation technology using such a receiving device is an important common basic technology in various fields such as navigation, security, recreation, or the like. However, the location estimation technology based on the GPS measurement requires a long time for synchronization at the time of activation, and also, the technology is difficult to use indoors or underground where a wireless signal from a satellite does not reach.
Further, a technology for a Personal Handyphone System (PHS) to measure the signal strength of a signal transmitted from a base station and to estimate the self location based on the measured signal strength is disclosed in, for example, Patent Document 1. Specifically, a base station of the PHS is installed by a communications firm, and thus, the installation location is usually known. Accordingly, by measuring the signal strengths of signals transmitted from 3 or more base stations and estimating the distance between each of the base stations and the self location based on the measured signal strengths, the PHS can estimate the self location by the principle of triangulation based on the installation location of each of the base stations.
Further, a location estimation method is also conceivable in which a wireless terminal that performs wireless communication with a base station (access point) in a wireless local area network (LAN) measures the signal strength of a signal transmitted from the wireless base station, and a location estimation device capable of communicating with the wireless terminal estimates the location of the wireless terminal based on the signal strength. For example, the base station in the wireless LAN transmits a beacon at regular intervals (for example, 5 times per second) for announcing the presence of the base station in the wireless LAN to the surrounding area. The wireless terminal transmits the signal strength of such a beacon to the location estimation device, and the location estimation device can estimate the location of the wireless terminal based on the signal strength and the location of the base station in the wireless LAN that is registered in advance. According to the location estimation method described above, since the base station in the wireless LAN is also installed indoors or underground, location estimation indoors or underground which has been difficult with the location estimation technology based on the GPS measurement is possible. That is, it can be said that the location estimation method described above is a location estimation technology superior in convenience and simplicity provided base station information indicating the location of the base station in the wireless LAN installed in the periphery of the wireless terminal is registered in the location estimation device.    [Patent Document 1] JP-A-2006-171012